This invention relates generally to multi-stage barrel type centrifugal pumps having a plurality of interstage pumping assemblies wherein the components are made of dissimilar materials so connected and disposed that during the operation of such pumps relative movement occurs in the interstage pumping assemblies with variations in temperatures and more particularly to a compensator for differential expansion in such centrifugal pumps adapted to permit relative movement between such interstage pumping assemblies while maintaining tight seals between adjacent interstage pumping assemblies.
Multi-stage barrel type centrifugal pumps include, an outer cylindrical or barrel type casing closed at one end by a first end casing and at the opposite end by a second end casing. A shaft extends end to end through the centrifugal pump along the longitudinal axis thereof and mounted on said shaft and in the outer casing are a plurality of serially connected interstage pumping assemblies the first of which communicates with and receives fluid to be pumped from an inlet generally in the first end casing and the end most or last of which interstage pumping assemblies communicates with a discharge outlet which can also be disposed in the first end casing, for delivering the pumped fluid from the centrifugal pump.
Multi-stage barrel type centrifugal pumps of the type above described are well known to those skilled in the art.
It is also known that the components and elements of such multi-stage barrel type centrifugal pumps are made of dissimilar materials. Hence in the operation of these pumps particularly when handling liquids at elevated temperatures forces are set up between the elements and components due to differential expansion which occurs with variations in temperatures of the liquids being pumped. If these forces are not restrained to some degree faulty pump performance may result. If restrained to severely excessive stresses in one or the other of the elements or components ultimately results in a failure of one or more of such components.
Further in the operation of multi-stage barrel type centrifugal pumps the interstage pumping assemblies expand differently compared with the surrounding outer casing and as a result there is a reduction in the tightness of the seals between such interstage pumping assemblies.
Heretofore the prior art have overcome this reduction in sealing tightness between interstage pumping assemblies in these centrifugal pumps by providing a sliding joint between the interstage pumping assemblies but it has been found that such sliding joints are susceptible to failure because of local corrosion or due to the accumulation of dirt between the coacting faces of the sliding joints.
Certain prior art shows means for excerting controlled axial forces against the interstage pumping assemblies for purposes non-analogous to those in the present invention as is indicated by U.S. Pat. Nos. 4,098,558 and 3,801,217.
The present invention seeks to provide an improved means for overcoming the above outlined problem in multi-stage barrel type centrifugal pumps by utilizing a compensator for this differential expansion which is capable of undergoing resilient displacement and which can be positioned in the centrifugal pumps between the outer casing and the interstage pumping assemblies so as to permit differential movement to occur between the interstage pumping assemblies while still exerting a controlled force between these interstage pumping assemblies so as to maintain the seals therebetween.